Ganglioside changes in the chicken optic lobes and cerebrum during embryonic development : Transient occurrence of "novel" multisialo-gangliosides.

The developmental profiles of 15 different gangliosides of the optic lobes and cerebrum of the chicken were followed from the 6 th day of incubation to hatching and correlated to morphological development. Five of these gangliosides appearing in both structures between the sixth and tenth day, have not been reported previously in higher vertebrates. Three chromatographed on TLC-plates similarly to G, G, and G gangliosides, which have been demonstrated in fish brain. One fraction moved just below G and is suggested, to contain G. These "novel" gangliosides, which are possibly related to a recently proposed separate and probably phylogenetically older biosynthetic pathway, contained up to 20% of total ganglioside sialic acid. The fifth "novel" fraction, containing up to 16% of total ganglioside-sialic acid, moved below the penta-sialoganglioside G and is suggested to contain hexa-sialogangliosides.There were two main changes in ganglioside synthesis, which were identical in both structures.The first occurred from the sixth to the eleventh day, parallel to decreased proliferation, maximal cell migration and neuroblast differentiation, G and G decreased rapidly in favour of G, G, and to the "novel" fractions, described above.The second occurred from the eleventh to the eighteenth day, parallel to increased growth and arborization of dendrites and axons as well as functional establishment of synaptic contacts, there was a sharp rise in the amount of G, G, and G. Concomitantly the "novel" gangliosides decreased. At hatching G was the predominant ganglioside. G, G, and G were always minor fractions, each accounting for less than 4% of total ganglioside-sialic acid. G was never detected, indicating neglegible myelinisation until hatching.